Nick Bollettieri, an American coach who trained the likes of Maria Sharapova, Andre Agassi, and the Williams sisters, has passed away at the age of 91. Born in 1931 to parents who were Italian immigrants, Bollettieri played a big role in revolutionising tennis-coaching, and the sport as a whole, in the United States. He then set up the Nick Bollettieri Tennis Academy in the early 1980s, where he coached so many people who became tennis stars later on. 

Although not having been a pro tennis player himself, only meddling in the sport at some point, Bollettieri was able to mold great talents, and his presence in the American tennis scene was very defining, and it is hard to imagine what pro tennis, at the world level, would have been like without his influence on tennis stars in the United States. 

He was the first to propose the idea of a live-in tennis bootcamp, and his training academy offered young players a place to practice and train for competitions. The academy was later bought by International Management Group (IMG) in 1987,  but he continued to play big roles in the academy, as well as coach some top players. 

Some of the players who attended his academy include Andre Agassi, Monica Seles, and Jim Courier, all of whom were ranked world number one at some point in their careers. Other top-ranked players he has been associated with include Maria Sharapova, Max Mirnyi, Jelena Jankovic, Venus, Serena Williams, and Boris Becker. Indeed, many of the players he had been involved with rose to the top of their careers.